We thought we knew all there was to know about AMD’s Tonga silicon, but it seems more information is coming to light. We first thought that Tonga had a 256-bit wide memory interface as the Radeon R9 285, which is based on Tonga does. But it turns out that the Tonga silicon actually has a 384-bit wide GDDR5 memory interface. On the R9 285 the Tonga die was placed on a package with pins for just 256-bit.
This means that the Tonga silicon can be placed on a larger package with more pins to wire out the full memory bus. This means that future Tonga-based SKUs could have 50% more memory bandwidth than the current generation (R9 285).
This is not the first time we have seen AMD do this. Their Tahiti LE chip was a Tahiti die placed on a smaller package with pins for just a 256-bit wide memory bus. This chip was featured on the Radeon HD 7870 XT.